Officials say Dawn M. Nguyen bought the firearms William Spengler used to kill two volunteer firefighters in Webster, N.Y., on Christmas Eve. Spengler also injured three others before killing himself.

A wreath serves as a tribute to the victims at the site of the Christmas Eve… (Guy Solimano / Getty Images )

WASHINGTON — A former neighbor of the Webster, N.Y., sniper who killed two volunteer firefighters on Christmas Eve illegally bought the guns used in the killing, federal authorities charged Friday.

Dawn M. Nguyen, 24, of Greece, N.Y., was charged in federal court with acting as a straw purchaser for William Spengler, who as a felon could not legally buy guns for himself. Spengler was convicted of killing his grandmother in 1980. Nguyen also faces state felony charges on allegations of falsifying business records.

U.S. Atty. William J. Hochul Jr. said Nguyen purchased a Bushmaster .223 semiautomatic rifle and a Mossberg 12-gauge shotgun from the Gander Mountain store in Rochester on June 6, 2010. But in truth, he said, she "knowingly made a false statement in connection with the purchase of the two firearms" and actually was acquiring them for Spengler.

She did not immediately enter a plea in the more serious federal case, in which she could face 10 years in prison and a $250,000 fine.

Spengler fatally shot himself after killing volunteer firefighters Michael Chiapperini and Tomasz Kaczowka and wounding two other firefighters and an off-duty police officer.

Authorities say Spengler created a ruse by setting his car on fire in a blaze that spread to his home and six other houses on Lake Road in Webster. Spengler then opened fire on the emergency crew as they arrived at the neighborhood on the shore of Lake Ontario.

Sean J. Martineck, a special agent with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said in a court affidavit that authorities learned of Nguyen from a suicide note Spengler left behind in which he said he obtained the weapons from his neighbor's daughter.

Nguyen lived next door to Spengler in 2008, two years after he was paroled from prison for killing his grandmother.

When officials spoke with Nguyen, Martineck said, she admitted that Spengler accompanied her to the gun shop and that he "picked out the firearms Nguyen purchased." But she said she wanted the weapons for her own personal safety and that they later were stolen from her vehicle. She never reported them stolen, however.

Finally, Martineck said, Nguyen "admitted that she purchased the guns for the guy who was her old neighbor," even though on the federal purchase form she had stated the weapons were for her own use.